Mechanical agitator



March 6, 1956 C. B. KINLEY I2 FIG. I. l4

FIG. 2. I

2 Sheets-Sheet 1 INVENTOR ATTORNEYS United States Patent MECHANICAL AGITATOR Clifford B. Kinley, Fort Lauderdale, Fla.

Application September 29, 1952, Serial No. 312,064

7 Claims. (Cl. 259-128) This invention relates to improvements in mechanical vibrator agitators and has, as its object, provision of means for vigorously agitating the contents of a receptacle. My invention employs new and novel principles to trans mit power at a distance from the exciting electro-magnet, and means for producing rotation and maximum turbulence of the liquid being agitated.

One application of the invention is as a mixer for preparing drinks such as malted milk. Another application is for agitating the liquid contents of a dishwasher. Further applications are the mixing of chemicals in numerous processes in the chemical industry.

A principal object of the invention is to provide a simple and efilcien't agitator which can be manufactured at a substantial lower cost than existing conventional motor operated types.

Another objective is to provide a vibrator type agitator which will deliver suflicient power with the vibrator arm extending down into the liquid far enough to give thorough mixing and aeration.

Another objective is the elimination of frictional bearings which require lubrication with possible consequent contamination of the liquid.

Another objective is an agitator, the electrical parts of which may be hermetically sealed, thereby eliminating any possibility of the liquid entering the electrical circuits and causing failure or shock to the operator.

Another objective is a device which may either be held in the hand or supported on a stand. Another objective is a device in which the agitator member may be easily removed for cleaning. A still further objective is an agitator which will provide vigorous agitation and rotation regardless of the size of the containing receptacle.

. The present invention utilizes a mixer having an agitator blade enjoying at lea-st two principles, not heretofore used in any mechanical device involving a resonant vibrator. These are the use of a standing wave mechanical vibrator for transmitting power, and a novel means of proeither by a pulsating or alternating electric current, and

operate on the fundamental or natural frequency of the combined mass and spring system. None of them have a nodal or stationary point on the vibrator except at the clamped end. The vibration is extended some distance from the armature by using a light stili arm set edgewise to the direction of vibration, the extended arm being a part of the total system which vibrates at the fundamental frequency or mode 1 as will be described. There is no node or standing wave for transmitting power, and the whole system vibrates, except the clamped end. A second method employed in several jig saw devices is the use of a sort of link system. Power is supplied by a heavy vibrating spring and armature with the light jig saw connected between the armature and another spring. Here 2 again the Whole system vibrates with no nodal or stationary points except at the clamped terminals.

In my device the power is transmitted by a standing mechanical wave to the end loop section where it is employed for useful work. The means for producing rotation is the combination of vibration in a straight line with the reaction force of the liquid having a component at right angles to the vibrator motion,.hence giving a resulting elliptical path to the working end of the vibrator blade. By making the blade thin and flexible and set at a small angle with the direction of vibration one can match the impedance of the vibrator to that of the liquid. The action is much the same as in a radio transmission or telephone transmission line, in which the maximum power transfer takes place only when the receiving device matches the transmission line. I have found by experiment that when the blade is too stiff or the angle of attack too great, the damping effect from the liquid is above the critical point and the amplitude of vibration is almost nil. When the impedance is matched correctly, however, by providing both the correct angle and the right mount of flexibility, there is very little reduction of the amplitude of vibration, and at the same time the transfer ofpower is large, producing the maximum amount of rotation and turbulence. The blade must not be made too thin because it will then flutter and bend instead of oscillating as a loop section. t

The foregoing objects and principles of my invention will be more readily seen from the following description and accompanying drawings in which:

Figure 1 is a front perspective view of my new agitator when used as a mixer,

Figure 2 is a rear perspective viewof the device of Figure 1,

Figure 3 illustrates the application of my invention to a dishwasher device,

Figure 4 is a side view in cross section of one form of my agitator device,

Figure 5 is front view of the mechanism of Figure 4, illustrating the use of a tapered width blade in accordance with the present invention,

Figure 5a illustrates a uniform width blade such as may be employed in the present invention,

Figure 6a illustrates the mode 1 vibration utilized by prior art devices, Figure 6b illustrates the mode 2 operation of the present invention, and Figure 60 illustrates the movement of the tip of my form of agitator blade due to the angle of incidence of the blade and the reaction forces of the liquid being mixed.

Referring now to Figures 1 and 2, member 10 is a supporting stand consisting of a base with an upright member slotted at its upper end. A cradle 20 is fastened to the slotted upright member by means of a bolt 31 and wing nut 32 so that the height thereof my be adjusted as desired. The cradle 20 contains a rubber pad 30 on which the operating mechanism rests in order to reduce vibration. A receptacle 17 for holding material to be mixed is placed on stand 10, and the agitator blade 9 extends from driving mechanism 11 into said receptacle.

The operating mechanism is more clearly seen by reference to Figures 4 and 5. A case 11 of non-magnetic nraterial houses a coil 7 for the production of an alternating flux field. The coil 7 fits over the central projection of a core 5 made of the usual laminated magnetic steel in the shape of an E. One end of the E is butted against a block 6 which closes one end of the electroag zaasils as spring brass or Phosphor bi'onze, and an armature of magnetic material. Theagitator blade 9 may be of uniform cross dimensionbut preferably is tapered from the clamped end 14 down to a praximneiy tliefltiwer third portion where it is given a sharp twist through 90 degrees at a nodal point 15 as explained later. Figure 5 specifically illustrates such a tapered width blade. Aii alternative blade structure of u'niformwidth is illustrated in Figure 5a and it will be seen, as before, that the blade 9 (Figure 5a) is also twisted at a nodal point 15'. Both the uniform and tapered width blades are conte'rnplated by the present invention, and while the following description refers particularly to blade 9, an analogous discussion applies to blade 9'. Returning how to Figure 5, it will be see'nthat from the nodal point 15 to the end of the blade 18, the blade width is held constant but the thickness is reduced sufficiently to make the blade flexible so that it Will bend from the reaction of the liquid. This portion of the blade is also givena slight twist preferably inthe reverse direction of the 90 degree twist so that it makes an anglefwith the direction of the vibration of approximately 10 degrees (3 to 25 degrees can be used depending on the stiffness of the blade).

A knob 12 serves as a handle when the operating unit is held by hand. The interior of the case 11 is filled with insulating compound so that it is hermetically sealed. This insulating compound, as well as a wedge 16, helps to hold .the ele'ctro-magnet in its correct position. A switch 24 and a cord 25 connect a power source to the coil 7.

Referring now to Figure 3 application of the above type of agitator to a portable dishwasher is indicated. The agitator unit, of the same general construction as previously described, is mounted on the under side of a lid 28 which covers a receptacle 29. A Wire dish-rack 40 for holding the dishes is placed within the receptacle 29, this rack being removable from the receptacle and so constructed as to keep the dishes from coming in contact with the agitator blade 9 in center. A rubber gasket 21 fits over the rim of receptacle 29 and cushions the vibration coming from the operating unit mounted on the lid. This gasket also serves to keep the dishwasher from splashing outside the container.

Figures 6a-c explain the method of operation of the agitator blade. Figure 6a shows the fundamental mode of vibration of a bar or reed with one end clamped and the other end free. This fundamental mode of vibration, which I shall refer to as mode 1, is a transverse bending back and forth of the bar in simpn harmonic motion. The shape of the bar in either direction from the normal position is a quarter sine wave. This resonant or natural frequency of mode 1 can readily be determined by experiment, or it may be calculated if the constants of the material are known. One suitable formula for this purpose is EI cor-3.52 M1 in which (01 is the angular velocity of the vibration in radians per second, E is the modulus of elasticity, I the moment of inertia ,u. the mass per unit length, and l the length. The frequency in cycles per second may be obtained by dividing the angular velocity in radians by 21r. Such a bar may be made to vibrate at higher overtone frequencies by exciting it with a periodic force of the same frequency as the overtone.

Figure 6b shows the first overtone or mode 2 vibration, as is used in the present invention, for a bar of uniform width and thickness and material as indicated for mode 1. In this case the bar vibrates with a standing wave having one nodal point and two anti-nodes or loops. The end loop for a uniform bar is approximately .22 of the overall length of the free portion of the bar. The frequency of vibration for this mode of vibra tion can easily be determined by experiment or by calcu by the arrows in Figure 6c.

4;. lation in the same manner as for mode 1. formula with the same symbols as above is By solution of this formula, it will be seen that 4 Elena 2 From these two formulas for wt and wz it is evident that for a given bar with no change in length the frequency of the first overtoneor mode 2 operation will be 22.4 divided by 3.52 or 6.367 times the fundamental or mode 1. By the same reasoning if two bars are adjusted in length so that the fundamental of one has the same frequency as the overtone or mode 2 of the other, then the length of the mode 2 bar will be equal to the or 2.52 times that of the mode 1 bar. Employing mode 2 operation will therefore extend the length of the agitator blade by two and one half times the mode 1 operation. Higher overtones are possible but unnecessary for this application. The employment of mode 2 transmits the power to the en'dloop without any losses other than that of the friction of bending and of the surrounding medium.

I prefer to use a tapered bar in order to increase the amount of power stored in the .vibrator, which then acts much the same as a fiy-wheel. This also assists in match ing the impedance of the liquid. Since the impedance uttered by a liquid is much greater than that of the atmosphere, it is necessary to reduce the surface area beating against the liquid. By making the bar smaller or of less width and thinner in the end loop portion it receives less reaction from the liquid thus tending to allow a much greater amplitude of vibration. Also by making the end loop narrow and thin its inertia is decreased thus making the length longer with greater amplitude of vibration and better adaptation for agitation. The length of the entire blade 9 is adjusted to give resonance on the first overtone or mode 2 operation corresponding to the exciting current, which is normally 60 cycles in the United States. This results in an operating frequency of cycles for the vibrator since there is a downward pull on the armature for both the positive and negative portions of the current cycle. N i

The manner of producing the rotation of the liquid and the cause of the vigorous turbulence is indicated in Figure 60. Since the blade is set at a small angle with its direction of vibration it will have a component of force F on the liquid in two directions. One component A--B will force the liquid in the same direction as the vibration, and this component will be in opposite directions for the up and downstrokes of the blade. The second component of force F-F against the liquid is at right angles to the direction of vibration. On the up stroke it will tend to push the liquid to the left, but at the same time, if the blade is flexible the blade will be pushed to the right. On the down strokeexactly the opposite happens, and the blade is pushed to the left. Consequently the combination of the vibration up and'down and the bending to right and left will give the blade tip an elliptical orbit. The rapid motion of 120 elliptical revolutions per second sets up a 'violent turbulence at the end of the blade producing a partial vacuum which sucks air down through the center of the rotation. The rotation of the liquid will always be opposite to the direction of the twist of the blade. For instance if the blade is set clockwise the liquid will rotate counterclockwise as indicated This rotation takes place reg'ardless of the size and shape of the containing receptacle.

Having thus described my invention, I claim:

A suitable 1. In a vibrator agitator device, an electromagnet producing an alternating flux field, an elongated agitator blade having a first end clamped adjacent said electro-magnet within said fiux field and having its other end extending beyond said flux field and into a liquid being agitated, the length of said blade being substantially defined by the where l is the length of said blade, E is the modulus of elasticity of said blade, I is the moment of inertia of said blade, ,u is the mass per unit length of said blade, and w is the angular velocity of vibration of said flux field, said blade being so vibrated by said flux field that a standing wave is produced, on said blade, having a node point between the ends thereof, said blade being twisted to the direction of vibration through a portion of the length thereof adjacent the unclamped end whereby the vibratory forces of said flux field and the reaction forces of said liquid cause the unclamped end of said blade to describe an elliptical path.

2. In a vibrator agitator, a supporting member comprising a base and an upright member affixed thereto, a platform slidably mounted on said upright member parallel to said base, an electro-magnet removably supported upon said platform and spaced therefrom by resilient means, an elongated agitator blade clamped at one of its ends adjacent said electromagnet and having its other unclamped end extending into a liquid to be agitated, said blade being resonantly vibrated under the influence of said electromagnet in a standing wave configuration which includes a nodal point between the clamped and the unclamped ends of said blade, said blade being twisted through an acute angle to the direction of said vibration between said nodal point and said unclamped end.

3. In a vibrator agitator device, a substantially fiat elongated vibrator blade of flexible magnetic material, a supporting structure, said blade being fixedly attached to said supporting structure, at one of its ends and having a free end extending into a material to be agitated, alternating flux producing means adjacent said fixedly attached 6 blade end for vibrating said blade in a standing wave configuration with a node point thereon closer to said free end than to said fixedly attached end, said blade being twisted, at said node point, at an angle to the direction of vibration effected by said flux producing means, whereby the free end describes a substantially elliptical path due to the vibratory forces of said flux producing means and to the reaction forces of the material being agitated.

4. The device of claim 3 in which said blade is substantially uniform in width throughout the length thereof, said node point appearing substantially .22 the length of said blade from the free end thereof.

5. The device of claim 3 in which said blade is tapered in width from said fixedly attached end to said free end.

6. In a vibrator agitator device, a substantially flat elongated fiexible vibrator blade including magnetic material adjacent one end thereof, a supporting structure, said one end of said blade being fixedly attached to said supporting structure whereby said blade comprises a cantilever depending from said supporting structure and having a free end extending into a material to be agitated, alternating flux producing means adjacent said fixedly attached blade end for vibrating said blade at its natural frequency in a predetermined plane whereby said blade exhibits a substantially non-vibrating node point thereon closer to said free end than to said fixedly attached end, said blade being twisted at an angle to said predetermined plane from said node point to said free end whereby the said free end describes a substantially elliptical path in said material being agitated due to the vibratory forces of said flux producing means and to the reaction forces of the said material being agitated.

7. The device of claim 6 wherein said blade is tapered in width from said fixedly attached end to said free end thereof.

References Cited in the file of this patent UNITED STATES PATENTS 

